The human body is exposed to a natural basic burden of toxic substances and is therefore confronted with a multiplicity of mutagenic and carcinogenic substances which, in the course of intrinsic metabolism, are even partly formed by the latter itself.
Man, however, has various defence mechanisms available on an immunological, cellular and genetic plane in order e.g. to counteract an allergic reaction, cell damage or a mutation event in the area of genetic information. Thus, in the cells, for example, so-called "repair systems" exist with whose aid changes in genetic material can be recognized and eliminated.
For a long time, it was assumed that there is a direct causal relationship between the action of possible risk factors such as e.g. various products of incomplete combustion, different radiations and/or electromagnetic fields, some plant protection agents and wood preservatives, certain mineral fibres (e.g. asbestos) and certain metabolic products of mould fungi (e.g. aflatoxin) on the human body and carcinogenesis. The fact that the majority of people who are exposed to these risk factors do not have the symptoms to be expected has led, however, to a rethinking in risk assessment. Thus the size of the cancer risk can no longer be defined on its own by the potential harmful substance or exposure factor. It must rather be assumed that it is the result of a multifactorial interrelationship between a multiplicity of substances/mechanisms which have an effect and the burdened body. It is further regarded as confirmed that several mutation events are necessary at certain sites in the genome in order that an abnormal cell having uncontrolled growth can be formed from a normal body cell.
Particular importance is ascribed to the body's own defence system, which can also be individually affected by the way of life. Thus, e.g. the absorption of food in the body initiates a number of chemical reactions in which substances having mutagenic and antimutagenic effects are in a close interrelationship with one another.
In the meantime, chemical compounds have been identified which have a protective action against substances having a mutagenic effect, such as e.g. different vitamins, mustard oils and beta-carotene. Naturally occurring plant phenols contained in foodstuffs, such as e.g. hydroxycinnamic acids and their compounds are also discussed as antimutagenic and anticarcinogenic substances of different intensity on account of their antioxidative properties (Karl Herrmann, "Hydroxyzimtsaure-Verbindungen als biologisch aktive Inhaltsstoffe von Lebensmitteln" Hydroxycinnamic acid compounds as biologically active constituents of foodstuffs!, Ernahrungs-Umschau 38, No. 4, pp. 148-154 (1991)). These findings are supported, inter alia, by epidemiological results, which enable an inverse relationship to be detected between the consumption of fruit and vegetables and various carcinoses.
The term "tobacco products" used in this description is to be understood as meaning both cigarettes, cigarillos and tobacco cartridges (so-called tobacco-"rolls") with or without a filter and fine-cut and pipe tobacco, which consist entirely or proportionally of tobacco and/or another smokable material, and also smoking materials resembling tobacco products, such as, for example, "Kretek" cigarettes with addition of up to 50% by weight of smokable spices, or pure, tobacco-free plant cigarettes.
It is known that the consumers of smokable tobacco products also absorb a multiplicity of organic compounds, of which some have a toxic potential for the human body and others, on the other hand, can reduce this. In the discussion about the health-endangering properties of tobacco products, for a long time in particular the mutagenic and cancer-promoting action of some of the tobacco constituents passing into the human body by means of inhalation has been given prominence. As already mentioned, however, there is no direct causal relationship between the action of harmful substances and carcinogenesis.
Numerous series of experiments have led to the result that the substances or compounds present in a tobacco product and passing into the body of the consumer either in the gas or particulate phase of the mainstream smoke are not by direct means able to transform a normal cell of the human body into an abnormal cell.
It is therefore to be found that the mutagenic action detectable in laboratory experiments of constituents of the mainstream smoke of tobacco products cannot immediately be equated with a carcinogenic effect, as most substances and substance groups to be mentioned in this connection display their endangering potential only as a result of the cell's own metabolism of these compounds. These findings about the mutagenic action were obtained with the aid of the generally known Ames test (D. M. Maron and B. N. Ames, "Revised Methods for the Salmonella Mutagenicity Test", Handbook of Mutagenicity Test procedures, Elsevier Science Publishers BV, Ed. B. J. Kilbey, M. Legator, W. Nichols and C. Ramel, 1984).
Until now different routes have been taken to reduce the risk potential of smokable tobacco products.
On the one hand, new filter systems were provided by means of which certain groups of harmful substances are prevented from passing into the mainstream smoke and thus into the respiratory tract of the consumer. Thus, for example, DE Patent 35 32 618 discloses a doping of the filters of filter cigarettes with, for example, L-ascorbic acid, by means of which the reduction of aldehydes in the mainstream smoke of cigarettes should be significantly favoured. From WO 89/01301, it is known to prepare filters of filter cigarettes with micro- and macrocapsules containing ethanol and other alcohols in order to protect the lung tissue from certain toxic constituents of the cigarette smoke such as, in particular, nitrosamines by prior "blocking" of the affected or accessible areas with certain alcohols released in the mainstream smoke.
It has furthermore been attempted to impregnate the tobacco of filter cigarettes with certain substances in order even to reduce the content of certain harmful substances in the mainstream smoke. It is thus known from OE Patent 340 297 and OE Patent 240 298 to treat tobacco with ascorbic acid or with salts thereof in order to reduce the nitrogen dioxide content of the cigarette smoke. Furthermore, according to EP Patent 0 116 085, a process for the impregnation of filter cigarettes with interferon or biologically active fragments thereof was disclosed. Cigarettes treated in this way should activate the body's own production of interferon and thus assist the immune system.
Products prepared in this way indeed contribute to reducing potential risks of smoking, but they also comprise disadvantages inherent to the system. On the one hand, only certain toxic constituents mainly of the gas phase of the cigarette smoke are retained by means of chemisorption in the unburnt section of the cigarette rod (NO.sub.2) or in the filter (aldehydes) while the content of other harmful substances in the mainstream smoke, however, is not affected. On the other hand, the production of a "protective layer" within the body according to WO 89/01301 should in turn only be successful against certain harmful substances such as, for example, the nitrosamines. The use of interferon according to EP Patent 0 116 085, however, is associated with considerable costs.